Orthopedic researchers from Thailand have dug into one test’s ability to assess whether patients recovering from total knee arthroplasty (TKA) can perform certain movements and tasks.
2-Minute Walk Test as Good as WOMAC? Or Oxford?
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The team compared the 2-minute walk test (2mwt) to the modified Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS), modified Knee Score (modified KS), Numerical Pain Rating Scale (NPRS) and Timed Up and Go Test (TUG).
Their research, “Validity and Responsiveness of the 2-Minute Walk Test for Measuring Functional Recovery after Total Knee Arthroplasty,” is published in the January 21, 2018 edition of the Journal of Arthroplasty.
Aasis Unnanuntana, M.D., with the Department of Orthopaedic Surgery at Mahidol University in Bangkok, Thailand and co-author on the study, told OTW, “In general, the level of impairment in patients with knee OA [osteoarthritis] and after TKA can be measured using validated patient-reported outcome measures (PROMs), which can be categorized into disease-specific questionnaires (such as WOMAC, OKS and the modified KS) and generic, quality-of-life questionnaires (such as the SF-36).”
“Although PROMs provide information on how individuals perceive their physical function in their own environment, it does not describe their ability to perform a specific task or action.”
“In addition, some investigators have demonstrated that the scores from PROMs taken before and after arthroplasty can overestimate patients’ actual functional capacity.”
“Given that PROMs may overestimate the functional status after joint arthroplasty, some investigators have advocated the use of performance-based tests e.g. 6-minute walk test or timed get-up-and-go test as another outcome measure.”
“This is a prospective cohort study, collecting data from TKA patients who were treated by a single surgeon and followed the same postoperative protocol. This study provides follow-up data at baseline, 3-month, 6-month and 12-month periods for most patients.”
“Both scores from PROMs (WOMAC, OKS, modified knee score) and performance-based tests (2-minute walk test and timed get-up-and-go test) improved significantly from baseline to 3, 6 and 12 months postoperatively. There were mild to moderate associations between the 2-minute walk test and modified WOMAC function subscales, and moderate to strong associations with OKS, indicating convergent validity of the 2-minute walk test with the functional outcome measures of PROMs.”
“A comprehensive evaluation should include a combination of PROMs and performance-based tests to better assess functional recovery in patients after a TKA. Performance-based tests are necessary to fully characterize the change in the physical function of patients after the TKA.”
“The 2-minute walk test is a valid performance-based test that is simple and easy-to-conduct. Thus, this test may be used routinely in clinical practice for evaluating functional recovery after a TKA.”
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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